After a five-year tenure that included the flawed rollout of the health care law and stormy relations with Capitol Hill Republicans, Department of Health and Human Services Secretary Kathleen Sebelius is resigning, a White House official said late Thursday.

President Barack Obama plans to nominate Sylvia Mathews Burwell, the director of the Office of Management and Budget, to replace Sebelius, the official said. Obama will make the announcement Friday at an 11 a.m. event at the White House where he will be joined by Sebelius and Burwell.

Sebelius, a former Kansas governor and insurance commissioner, was an early supporter of Obama’s, endorsing him during his hard-fought Democratic primary campaign against Hillary Rodham Clinton. The president turned to her to run the massive federal agency after his first choice for the job, former Sen. Tom Daschle, ran into confirmation problems. Sebelius became the face of the administration’s relentless campaign to reform the country’s health care system, appearing regularly before Capitol Hill panels and traveling the country seeking to win converts to the effort.

But she also became the face of the health law’s troubled rollout last October when the federal online insurance marketplace, healthcare.gov, suffered numerous technological problems that stymied enrollments and frustrated millions of potential customers. The administration eventually had to call in technology experts, who spent more than a month working around the clock to retool the site, which was relaunched in early December. But the catastrophic rollout threatened to undermine Obama’s legacy program. It also spurred numerous congressional oversight hearings at which Sebelius was called in to explain what went wrong to both exasperated Republicans and Democrats.

Still, after the recovery of the website, Obama was able to announce this month that more than 7 million people had enrolled in health plans on the marketplaces, the same number that the Congressional Budget Office had predicted before the website problems. Sebelius said Thursday enrollment had grown to 7.5 million.

That did not diminish Republican complaints. Sebelius testified before the Senate Finance Committee Thursday, and Republicans expressed frustration over her inability to provide more data about the people who have signed up for coverage through the marketplaces, or exchanges, and they were angry at the administration’s decision to postpone key implementation deadlines. Some Republicans, including Sen. Pat Roberts, from her home state of Kansas, have demanded she resign.

Comedians took aim as well, including Daily Show host Jon Stewart. In an Oct. 7 appearance – when the website was faltering, Stewart pulled a laptop out onto his desk and told Sebelius: “We&apos;re going to do a challenge. I’m going to try and download every movie ever made and you are going to try to sign up for Obamacare — and we’ll see which happens first.”

The White House official said Sebelius notified the president in early March of her decision. “She believed that once open enrollment ended it would be the right time to transition the Department to new leadership,” the official said.

“Through the passage and implementation of the Affordable Care Act, Secretary Sebelius has overseen one of the most consequential initiatives of this Administration; under her leadership, 7.5 million people have selected plans,” the official said. “Sebelius has also fought to improve children’s health, expand mental health care, reduce racial and ethnic disparities, bring us closer to the first AIDS-free generation, and promote women’s health. The president is deeply grateful for her service.”

In an interview Thursday with The New York Times, Sebelius said she knew that she would not “be here to turn out the lights in 2017.”

“My balance has always been, when do you make that decision?” she added.

Burwell, Obama&apos;s nominee to succeed Sebelius, helped the administration navigate the government shutdown in October. She served in the Clinton administration, worked for the Bill & Melinda Gates Foundation and is the former president of the Walmart Foundation.

Almost one year ago, the Senate voted 96-0 to confirm Burwell, which may help her chances for Senate confirmation to head HHS. In a tweet, Sen. John McCain, R-Ariz., said that Burwell “is an excellent choice to be the next #HHS Secretary.”

Republican reaction to Sebelius&apos; departure was mixed. Some lawmakers said the secretary&apos;s task was difficult from the start while others welcomed her exit.

“Anybody put in charge of Obamacare would be set up to fail. Secretary Sebelius was asked to promote something unready, poorly structured, and unpopular,” said Sen. Charles Grassley, R-Iowa. “She was given a law that was just about written in pencil the way the deadlines changed all the time. That put her in a position of having a strained relationship with Congress. It’s disingenuous for the White House to distance itself from the problems and attribute them to partisan sniping at one member of the Administration. The next secretary might have a fresh start with the public and Congress but the flawed law is still the law.”

Senate Minority Leader Mitch McConnell, R-Ky., said, “Secretary Sebelius may be leaving, but the problems with this law and the impact it’s having on our constituents aren’t. Obamacare has to go, too.”

But her service was applauded by Democrats. In a statement Thursday night, Sen. Jay Rockefeller, D-W.Va., said, “For the past five years, I have marveled at Secretary Sebelius&apos;s grace under pressure. She never backed down from the tremendous responsibilities of her position, which were of a magnitude no other cabinet secretary has ever had to face with regard to domestic policy. … Not once did she let attacks from both the left and the right deter her from the goal of bringing health care to millions of uninsured Americans, and working to improve the health of people across the nation.”

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